U.S. patent number 10,160,214 [Application Number 15/804,332] was granted by the patent office on 2018-12-25 for liquid ejecting apparatus.
This patent grant is currently assigned to Seiko Epson Corporation. The grantee listed for this patent is SEIKO EPSON CORPORATION. Invention is credited to Shunya Fukuda.
United States Patent |
10,160,214 |
Fukuda |
December 25, 2018 |
Liquid ejecting apparatus
Abstract
A liquid ejecting apparatus includes a liquid ejecting head
including a substrate where a plurality of hollow portions are
formed, a flexible plane that delimits a part of the hollow
portion, and a piezoelectric element provided corresponding to the
hollow portion, an inspection mechanism that inspects ejection of
liquid from a nozzle based on an electromotive force of the
piezoelectric element, and a signal generation circuit that
generates a first drive signal and a second drive signal. The
second drive signal maintains a state, where a second vibration
portion including the second piezoelectric element and the flexible
plane corresponding to the second piezoelectric element is
deformed, during a detection period in which the inspection
mechanism performs inspection based on vibration caused when a
first vibration portion including the first piezoelectric element
and the flexible plane corresponding to the first piezoelectric
element is driven.
Inventors: |
Fukuda; Shunya (Azumino,
JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
SEIKO EPSON CORPORATION |
Tokyo |
N/A |
JP |
|
|
Assignee: |
Seiko Epson Corporation (Tokyo,
JP)
|
Family
ID: |
62065254 |
Appl.
No.: |
15/804,332 |
Filed: |
November 6, 2017 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20180126738 A1 |
May 10, 2018 |
|
Foreign Application Priority Data
|
|
|
|
|
Nov 10, 2016 [JP] |
|
|
2016-219655 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B41J
2/0451 (20130101); B41J 2/04553 (20130101); B41J
2/025 (20130101); B41J 2/04588 (20130101); B41J
2/2142 (20130101); B41J 2/20 (20130101); B41J
2/19 (20130101); B41J 2/04581 (20130101); B41J
2/16579 (20130101); B41J 19/68 (20130101); B41J
19/66 (20130101); B41J 2/14201 (20130101) |
Current International
Class: |
B41J
2/165 (20060101); B41J 2/045 (20060101); B41J
2/025 (20060101); B41J 2/20 (20060101); B41J
2/21 (20060101); B41J 2/19 (20060101); B41J
2/14 (20060101); B41J 19/66 (20060101); B41J
19/68 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Jackson; Juanita D
Attorney, Agent or Firm: Workman Nydegger
Claims
What is claimed is:
1. A liquid ejecting apparatus comprising: a liquid ejecting head
including a substrate where a plurality of hollow portions are
formed, a flexible plane that delimits a part of the hollow portion
in the substrate, and a piezoelectric element provided
corresponding to and opposite to the hollow portion with the
flexible plane in between; an inspection mechanism that inspects
ejection of liquid from a nozzle that communicates with the hollow
portion based on an electromotive force of the piezoelectric
element caused by vibration generated when the piezoelectric
element is driven; and a signal generation circuit that generates a
first drive signal applied to a first piezoelectric element to be
inspected among a plurality of piezoelectric elements corresponding
to the plurality of hollow portions and a second drive signal
applied to a second piezoelectric element different from the first
piezoelectric element, wherein the second drive signal maintains a
state, where a second vibration portion including the second
piezoelectric element and the flexible plane corresponding to the
second piezoelectric element is deformed, during at least a
detection period in which the inspection mechanism performs
inspection based on vibration caused when a first vibration portion
including the first piezoelectric element and the flexible plane
corresponding to the first piezoelectric element is driven.
2. The liquid ejecting apparatus according to claim 1, wherein the
second drive signal is maintained at a constant adjustment voltage
during the detection period.
3. The liquid ejecting apparatus according to claim 2, further
comprising: a temperature detection mechanism that detects
temperature of the liquid ejecting head, wherein the adjustment
voltage varies according to the temperature detected by the
temperature detection mechanism.
4. The liquid ejecting apparatus according to claim 2, wherein the
second drive signal has a plurality of different adjustment
voltages.
5. The liquid ejecting apparatus according to claim 1, wherein the
second drive signal generates a waveform element that amplifies
vibration of the first vibration portion by vibrating the second
vibration portion during a vibration generation period in which the
first vibration portion is vibrated by the first drive signal
before the detection period.
6. The liquid ejecting apparatus according to claim 1, wherein the
first vibration portion and the second vibration portion are
adjacent to each other with a wall delimiting the hollow portions
in between.
Description
The entire disclosure of Japanese Patent Application No.
2016-219655, filed Nov. 10, 2016 is expressly incorporated by
reference herein.
BACKGROUND
1. Technical Field
The present invention relates to a liquid ejecting apparatus such
as an ink jet type recording apparatus, in particular to a liquid
ejecting apparatus that causes a nozzle to eject liquid by
generating pressure variation in liquid in a hollow portion that
communicates with the nozzle by deforming a vibration portion that
delimits a part of the hollow portion.
2. Related Art
The liquid ejecting apparatus is an apparatus that has a liquid
ejecting head and ejects (discharges) various liquids from nozzles
of the liquid ejecting head. An example of a typical liquid
ejecting apparatus is an image recording apparatus such as an ink
jet type recording apparatus (printer) that has an ink jet type
recording head (hereinafter referred to as a recording head) and
performs recording by ejecting ink in a liquid state as ink
droplets from nozzles of the recording head. Further, the liquid
ejecting apparatus is used to eject various types of liquids such
as color materials used for a color filter of a liquid crystal
display and the like, an organic material used for an organic EL
(Electro Luminescence) display, and an electrode material used to
form an electrode. A recording head for an image recording
apparatus ejects ink in a liquid state, and a color material
ejecting head for a display manufacturing apparatus ejects solution
of each color material of R (Red), G (Green), and B (Blue). An
electrode material ejecting head for an electrode forming apparatus
ejects an electrode material in a liquid state, and a bioorganic
material ejecting head for a chip manufacturing apparatus ejects
solution of bioorganic material.
For example, in the liquid ejecting apparatus described above,
there is a case where liquid is not normally ejected from a nozzle
of the liquid ejecting head due to factors such as clogging due to
thickening of liquid and foreign objects or bubbles existing in a
flow path, that is, a case where the amount or the speed of the
liquid ejected from the nozzle is different from an original target
value or the liquid is not ejected from the nozzle at all in the
worst case. Therefore, a technique that inspects whether or not the
liquid is normally ejected from all the nozzles is proposed. For
example, JP-A-2014-177127 discloses a technique that inspects
ejection abnormality of ink based on residual vibration of liquid
in a cavity (a hollow portion or a pressure chamber) when driving a
piezoelectric element.
In the liquid ejecting head described above, a plurality of
components such as a substrate where nozzles are formed and a
substrate where cavities are formed are bonded with adhesive or the
like. Therefore, a positional relationship between the cavities and
the piezoelectric elements and dimensions of components may be
different from target values due to variation in manufacturing or
an adhesive that bonds substrates together may extrude to a cavity
and attach to a flexible plane that delimits the cavity, so that
there is a case where a vibration period of a vibration portion
including a piezoelectric element and a flexible plane
corresponding to the piezoelectric element may be different from a
design target value (reference value). As a result, there is a risk
that inspection accuracy is degraded.
SUMMARY
An advantage of some aspects of the invention is to provide a
liquid ejecting apparatus that can improve detection accuracy of
ejection abnormality in a configuration that inspects the ejection
abnormality based on the residual vibration generated by driving
the piezoelectric element.
According to an aspect of the invention, the liquid ejecting
apparatus includes a liquid ejecting head including a substrate
where a plurality of hollow portions are formed, a flexible plane
that delimits a part of the hollow portion in the substrate, and a
piezoelectric element provided corresponding to and opposite to the
hollow portion with the flexible plane in between, an inspection
mechanism that inspects ejection of liquid from a nozzle that
communicates with the hollow portion based on an electromotive
force of the piezoelectric element caused by vibration generated
when the piezoelectric element is driven, and a signal generation
circuit that generates a first drive signal applied to a first
piezoelectric element to be inspected among a plurality of
piezoelectric elements corresponding to the plurality of hollow
portions and a second drive signal applied to a second
piezoelectric element different from the first piezoelectric
element. The second drive signal maintains a state where a second
vibration portion including the second piezoelectric element and
the flexible plane corresponding to the second piezoelectric
element is deformed during at least a detection period in which the
inspection mechanism performs inspection based on vibration caused
when a first vibration portion including the first piezoelectric
element and the flexible plane corresponding to the first
piezoelectric element is driven.
According to this invention, it is possible to change a tensile
force applied to the flexible plane of the first vibration portion
by causing the second vibration portion to be in a deformed state
during the detection period, so that it is possible to change a
vibration period of the first vibration portion. Therefore, when a
unique vibration period of the first vibration portion is different
from a design target value (reference vibration period) due to, for
example, manufacturing variation and the like, it is possible to
adjust (correct) the vibration period so as to be close to the
target value by using the second vibration portion. Thereby, it is
possible to improve the detection accuracy of ejection
abnormality.
In the configuration described above, it is preferable to employ a
configuration where the second drive signal is maintained at a
constant adjustment voltage during the detection period.
According to this configuration, the second vibration portion does
not vibrate and maintains a constant shape in a period of time in
which the first vibration portion vibrates in the detection period,
so that it is suppressed that the vibration of the second vibration
portion is superimposed on the vibration of the first vibration
portion to cause adverse effects.
Further, in the configuration described above, it is preferable to
employ a configuration where a temperature detection mechanism that
detects temperature of the liquid ejecting head is included and the
adjustment voltage varies according to the temperature detected by
the temperature detection mechanism.
According to this configuration, even when the vibration period of
the first vibration portion varies from the reference vibration
period according to variation of temperature, it is possible for
the second vibration portion to adjust the vibration period so as
to be close to the reference vibration period.
Further, in the configuration described above, it is preferable to
employ a configuration where the second drive signal has a
plurality of different adjustment voltages.
According to this configuration, it is possible to easily select a
more suitable adjustment voltage.
Further, in the configuration described above, it is preferable to
employ a configuration where the second drive signal generates a
waveform element that amplifies vibration of the first vibration
portion by vibrating the second vibration portion during a
vibration generation period in which the first vibration portion is
vibrated by the first drive signal before the detection period.
According to this configuration, it is possible to amplify the
vibration of the first vibration portion, so that it is possible to
further improve the detection accuracy of ejection abnormality.
Further, in the configuration described above, it is preferable to
employ a configuration where the first vibration portion and the
second vibration portion are adjacent to each other with a wall
delimiting the hollow portions in between.
According to this configuration, it is possible to more efficiently
change a tensile force which is applied to the flexible plane of
the first vibration portion by deformation of the second vibration
portion.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be described with reference to the accompanying
drawings, wherein like numbers reference like elements.
FIG. 1 is a perspective view for explaining a configuration of a
printer, which is one form of a liquid ejecting apparatus.
FIG. 2 is a cross-sectional view for explaining a configuration of
a recording head, which is one form of a liquid ejecting head.
FIG. 3 is a block diagram showing an example of an electrical
configuration of the printer.
FIG. 4 is a waveform chart for explaining a configuration of a
drive signal.
FIG. 5 is a schematic diagram of a recording head for explaining
inspection processing.
FIG. 6 is a schematic diagram of the recording head for explaining
the inspection processing.
FIG. 7 is a schematic diagram of the recording head for explaining
the inspection processing.
FIG. 8 is a waveform chart for explaining a configuration of a
drive signal in a second embodiment.
FIG. 9 is a waveform chart for explaining a configuration of a
drive signal in a third embodiment.
FIG. 10 is a schematic diagram for explaining inspection processing
in a fourth embodiment.
FIG. 11 is a schematic diagram for explaining inspection processing
in a fifth embodiment.
FIG. 12 is a schematic diagram for explaining inspection processing
in a sixth embodiment.
DESCRIPTION OF EXEMPLARY EMBODIMENTS
Hereinafter, embodiments for carrying out the invention will be
described with reference to the drawings. n the embodiments
described below, there are various limitations as preferable
concrete examples of the invention. However, the scope of the
invention is not limited to the embodiments as long as a
description limiting the invention is not given in particular in
the description below. In the description below, as the liquid
ejecting apparatus of the invention, an ink jet type recording
apparatus (hereinafter referred to as a printer 1) in which an ink
jet recording head (hereinafter referred to as a recording head 2)
that is a type of a liquid ejecting head is mounted will be
described as an example.
FIG. 1 is a perspective view showing a configuration of the printer
1. The printer 1 includes a carriage 4 where the recording head 2
is mounted and an ink cartridge 3 that is a type of a liquid supply
source that retains ink (a type of liquid) is detachably attached,
a platen 5 that is arranged below the recording head 2 that is
performing a recording operation, a carriage moving mechanism 7
that reciprocates the carriage 4 in a paper width direction of a
recording paper 6 (a type of a recording medium or a liquid landing
target), that is, in a main scanning direction, and a paper feed
mechanism 8 that transports the recording paper 6 in a sub-scanning
direction crossing (perpendicular to) the main scanning
direction.
The carriage 4 is attached in a state of being pivotally supported
by a guide rod 9 provided along the main scanning direction and
reciprocates in the main scanning direction along the guide rod 9.
The printer 1 is configured to be able to perform so-called
bidirectional recording which records characters and images on the
recording paper 6 in both directions including a forward direction
in which the carriage 4 moves from a home position that is a
standby position of the recording head 2 provided at one end (right
side in FIG. 1) of a moving range of the carriage 4 to the other
end opposite to the one end and a backward direction in which the
carriage 4 returns from the other end to the home position. It is
also possible to employ a configuration in which the ink cartridge
3 is arranged in a main body of the printer 1 instead of the
carriage 4 and ink in the ink cartridge 3 is supplied to the
recording head 2 through an ink supply tube.
FIG. 2 is a cross-sectional view showing an example of the
recording head 2. For convenience of explanation, a lamination
direction of members is defined as a vertical direction. The
recording head 2 of the present embodiment is formed by laminating
a plurality of substrates, specifically, a nozzle plate 11, a
communicating substrate 13, and an actuator substrate 12 in this
order and bonding and unitizing the substrates with an adhesive.
The actuator substrate 12 is formed by laminating a pressure
chamber forming substrate 14 (a type of a substrate in the
invention), a vibrating plate 15, a piezoelectric element 16, and
the like. A sealing plate 17 that covers and protects the
piezoelectric element 16 is laminated on the actuator substrate 12
and a laminated body of these is attached to a case 18, so that the
recording head 2 is formed.
The case 18 is a box-shaped member made of synthetic resin. A
housing hollow portion 19 that is recessed in a rectangular
parallelepiped shape from a lower surface of the case 18 to middle
of the case 18 in a height direction is formed on the lower surface
of the case 18. When the communicating substrate 13 of the
laminated body is bonded to the lower surface, the actuator
substrate 12 (the pressure chamber forming substrate 14, the
vibrating plate 15, the piezoelectric element 16, and the sealing
plate 17) of the laminated body is housed in the housing hollow
portion 19. An ink introduction passage 20 is formed in the case
18. Ink from the ink cartridge 3 is introduced to a common liquid
chamber 26 through the ink introduction passage 20.
The pressure chamber forming substrate 14 of the present embodiment
is made of a silicon single crystal substrate (hereinafter, also
referred to as simply a silicon substrate). In the pressure chamber
forming substrate 14, a plurality of pressure chamber hollow
portions, each of which is a pressure chambers 21 that is a type of
a hollow portion in the invention, are formed. An opening portion
on one side (upper surface side) of the pressure chamber hollow
portion in the pressure chamber forming substrate 14 is sealed by
the vibrating plate 15. The communicating substrate 13 is bonded to
a surface of the pressure chamber forming substrate 14 opposite to
the vibrating plate 15, and an opening portion on the other side of
the pressure chamber hollow portion is sealed by the communicating
substrate 13. Thereby, the pressure chamber 21 is delimited and
formed. Here, a portion where the upper opening of the pressure
chamber 21 is sealed by the vibrating plate 15 is a flexible plane
22 that is displaced when the piezoelectric element 16 (active
portion) is driven. It is also possible to employ a configuration
in which the pressure chamber forming substrate 14 and the flexible
plane 22 are integrated together. Specifically, etching is
performed from the lower surface of the pressure chamber forming
substrate 14 to leave a thin portion whose thickness is thin on the
supper surface, so that the pressure chamber hollow portion is
formed. It is possible to employ a configuration in which the thin
portion functions as the flexible plane 22.
The pressure chamber 21 of the present embodiment is a hollow
portion elongated in a direction (second direction) crossing a
direction in which nozzles 24 are arranged side by side in
parallel, that is, a nozzle row direction (first direction). One
end portion of the pressure chamber 21 in the second direction
communicates with the nozzle 24 through a nozzle communicating port
23 of the communicating substrate 13. The other end portion of the
pressure chamber 21 in the second direction communicates with the
common liquid chamber 26 through an individual communicating port
27 of the communicating substrate 13. A plurality of pressure
chambers 21 are arranged side by side in parallel while being
separated by partition walls 25 (see FIG. 5 and the like) along the
nozzle row direction (first direction) corresponding to each nozzle
24.
The communicating substrate 13 is a plate member made of a silicon
substrate in the same manner as the pressure chamber forming
substrate 14. In the communicating substrate 13, a hollow portion
to be the common liquid chamber 26 (also called a reservoir or a
manifold) provided in common for a plurality of pressure chambers
21 of the pressure chamber forming substrate 14 is formed by
anisotropic etching. The common liquid chamber 26 is a hollow
portion elongated along a direction in which the pressure chambers
21 are arranged side by side in parallel (that is, the first
direction). As described above, the common liquid chamber 26
communicates with each pressure chamber 21 through the individual
communicating port 27.
The nozzle plate 11 is a plate member in which a plurality of
nozzles 24 are provided in a row shape. In the present embodiment,
the nozzle row is formed by providing a plurality of nozzles 24 in
a row at a pitch corresponding to a dot formation density. The
nozzle plate 11 of the present embodiment is made of a silicon
substrate, and the cylindrically shaped nozzles 24 are formed by
dry-etching the substrate. Corresponding to each nozzle 24, an ink
flow path is formed from the common liquid chamber 26 described
above to the nozzle 24 through the individual communicating port
27, the pressure chamber 21, and the nozzle communicating port
23.
The piezoelectric element 16 is arranged on an outer surface of the
vibrating plate 15, which is opposite to the pressure chamber 21,
corresponding to each pressure chamber 21. The illustrated
piezoelectric element 16 is a piezoelectric element of a so-called
flexural vibration mode and is formed by a drive electrode and a
common electrode which are not shown in the drawings and which
sandwich a piezoelectric layer. When a drive signal (drive pulse)
is applied to the drive electrode of the piezoelectric element 16,
an electric field according to a voltage difference is generated
between the drive electrode and the common electrode. The electric
field is applied to the piezoelectric layer and the piezoelectric
layer is deformed according to the strength of the applied electric
field. Specifically, the higher the voltage of the drive electrode
is, the more a central portion in the width direction (nozzle row
direction) of the piezoelectric layer bends into the pressure
chamber 21 (toward the nozzle plate 11), so that the flexible plane
22 of the vibrating plate 15 is deformed so as to decrease the
volume of the pressure chamber 21. On the other hand, the lower the
voltage of the drive electrode is (the closer to 0 the voltage is),
the more a central portion in the short length direction of the
piezoelectric layer bends away from the nozzle plate 11, so that
the vibrating plate 15 is deformed so as to increase the volume of
the pressure chamber 21.
FIG. 3 is a block diagram showing an electrical configuration of
the printer 1. The printer 1 of the present embodiment includes a
printer controller 31 and a print engine 32. The printer controller
31 includes an external interface (external I/F) 33 to which print
data and the like are inputted from external apparatuses such as a
computer and a mobile phone, a storage unit 34 that stores a
control program and the like and various data and the like for
various controls, a CPU 35 that performs integrated control of each
unit according to the control program stored in the storage unit
34, and a drive signal generation circuit 36 (a type of a signal
generation circuit in the invention) that generates a drive signal
to be supplied to the recording head 2. The print engine 32 has the
recording head 2, the carriage moving mechanism 7, the paper feed
mechanism 8, a vibration detection circuit 38, a temperature sensor
40 (corresponding to a temperature detection mechanism in the
invention), and the like.
The drive signal generation circuit 36 outputs a drive signal COM
to be applied to the drive electrode of the piezoelectric element
16 and also outputs a common DC voltage VBS to be applied to the
common electrode of the piezoelectric element 16. The drive signal
generation circuit 36 is electrically connected to the drive
electrode of the piezoelectric element 16 through a pulse selection
switch 37 provided for each piezoelectric element 16. Further, the
drive signal generation circuit 36 is electrically connected to the
common electrode of the piezoelectric element 16 through a switch
39 provided in common for each piezoelectric element 16 belonging
to the same nozzle row and the vibration detection circuit 38
connected in parallel with the switch 39.
A head controller 30 of the recording head 2 performs ink ejection
control based on gradation data SI transmitted from the printer
controller 31. In the present embodiment, the gradation data SI
including two bits is transmitted in synchronization with a clock
signal and sequentially inputted into a shift register and a latch
circuit (that are not shown in the drawings) of the head controller
30. Then, the latched gradation data SI is outputted to a decoder
not shown in the drawings. The decoder generates pulse gradation
data for selecting a drive pulse included in the drive signal COM
based on a high-order bit group and a low-order bit group of
recording data.
The drive signal COM from the drive signal generation circuit 36 is
supplied to the head controller 30. The drive signal COM is
inputted into the pulse selection switch 37 of the head controller
30. The drive electrode of the piezoelectric element 16 is
connected to the output side of the pulse selection switch 37. The
pulse selection switch 37 selectively applies the drive pulse
included in the drive signal COM to the drive electrode of the
piezoelectric element 16 based on the pulse gradation data
described above. The pulse selection switch 37 functions as a
switching mechanism that switches a connection state or a
disconnection state between the drive signal generation circuit 36
and the piezoelectric element 16 when inspection processing
described later is performed.
The vibration detection circuit 38 connected in parallel with the
switch 39 is provided to the common electrode side of the
piezoelectric element 16. The switch 39 is switch-controlled
according to a switching signal CS outputted from the CPU 35. The
switch 39 is turned off during a detection period described later
and is turned on during the other period. The vibration detection
circuit 38 includes a detection resistor and an A/D converter which
are not shown in the drawings and outputs an electromotive force
signal of the piezoelectric element 16 based on vibration (residual
vibration during the detection period) generated in ink in the
pressure chamber when the piezoelectric element 16 is driven by an
inspecting drive pulse Pd shown in FIG. 4 to the printer controller
31 as a detection signal. The CPU 35 of the printer controller 31
inspects presence or absence of abnormality of ink ejection from
the nozzles 24 based on the electromotive force signal outputted
from the vibration detection circuit 38. Therefore, the vibration
detection circuit 38 and the CPU 35 function as an inspection
mechanism of the invention and perform inspection on the ink
ejection from the nozzles 24 by detecting vibration of ink in the
pressure chamber by using the piezoelectric element 16 as a
vibration sensor.
The printer 1 according to the invention is configured to perform
inspection processing of the recording head 2 so as to detect
ejection abnormality due to thickening of ink and the like. As an
inspection execution condition, it is possible to use a condition
that a usage time of the printer 1 (for example, an integrated
value of time while the printer 1 performs an operation to eject
ink from the nozzles 24), the number of ejection times (for
example, the sum of the numbers of ejection times of all the
nozzles or an integrated value of average values of the numbers of
ejection times of all the nozzles), or the total number of
recording media that have been printed exceeds a predetermined
determination value. Further, a case where execution of the
inspection processing is instructed by a user through a printer
driver or the like may be used as the inspection execution
condition. When the inspection execution condition is established,
the printer controller 31 proceeds to the inspection processing,
selects a nozzle to be inspected from all the nozzles 24 of the
recording head 2, and performs the inspection processing based on
an electromotive force generated in the piezoelectric element 16
corresponding to the nozzle to be inspected when applying, for
example, the inspecting drive pulse Pd shown in FIG. 4 to the
piezoelectric element 16. For example, the nozzle to be inspected
may be sequentially selected from a nozzle located at one end of a
nozzle row to a nozzle located at the other end of the nozzle row,
or for example, the nozzle to be inspected may be selected when a
user specifies a nozzle 24 suspected of ejection abnormality due to
thickening of ink.
As the inspection drive pulse described above, a pulse of various
waveforms can be employed if the pulse can give pressure variation
to the ink in the pressure chamber 21. However, in the present
embodiment, the inspecting drive pulse Pd shown in FIG. 4 is used.
Further, in the present embodiment, when an inspecting drive signal
COM1 (a type of a first drive signal in the invention) is supplied
to the piezoelectric element 16 to be inspected (corresponding to a
first piezoelectric element in the invention) corresponding to the
nozzle 24 to be inspected and inspection is performed by the
piezoelectric element 16, an adjusting drive signal COM2 (a type of
a second drive signal in the invention) is supplied to another
piezoelectric element 16 (corresponding to a second piezoelectric
element in the invention) different from the piezoelectric element
16 to be inspected, so that a vibration period of the piezoelectric
element 16 to be inspected and the flexible plane 22 (hereinafter
referred to as an inspection target vibration portion)
corresponding to the piezoelectric element 16 to be inspected can
be adjusted.
FIG. 4 is a waveform chart for explaining a configuration of the
inspecting drive signal COM1 and the adjusting drive signal COM2.
The upper waveform indicates the inspecting drive signal COM1 and
the lower waveform indicates the adjusting drive signal COM2. The
inspecting drive signal COM1 of the present embodiment is divided
into three periods, which are a first period T1, a second period
T2, and a third period T3. The inspecting drive pulse Pd shown in
FIG. 4 is generated in the second period T2. In the first period T1
and the third period T3 of these periods T1 to T3, the voltage of
the inspecting drive signal COM1 is constant at a reference voltage
VB (standby voltage). The beginning and the end of the inspecting
drive pulse Pd in the second period T2 are set to the reference
voltage VB. The reference voltage VB is a voltage corresponding to
a volume from which the pressure chamber 21 expands or contracts.
As described later, when the reference voltage VB is applied to the
piezoelectric element 16, the piezoelectric element 16 and the
flexible plane 22 corresponding to the piezoelectric element 16
bend toward the inside of the pressure chamber 21 (toward the
nozzle plate 11). The second period T2 is a vibration generation
period in which pressure vibration is generated in the ink in the
pressure chamber 21. The third period T3 is a detection period in
which the pressure vibration (residual vibration) of ink generated
in the second period T2 is detected by the vibration detection
circuit 38. The inspecting drive pulse Pd generated in the second
period T2 includes a preliminary expansion element p1, an expansion
hold element p2, a contraction element p3, a contraction hold
element p4, and a return element p5. The preliminary expansion
element p1 is a waveform element whose voltage changes toward a
ground voltage GND from the reference voltage VB to an expansion
voltage VL lower than the reference voltage VB. The expansion hold
element p2 is a waveform element which holds the expansion voltage
VL that is an end voltage of the preliminary expansion element p1
for a certain period of time. The contraction element p3 is a
waveform element whose voltage changes toward positive side from
the expansion voltage VL to a contraction voltage VH through the
reference voltage VB. The contraction hold element p4 is a waveform
element which holds the contraction voltage VH for a certain period
of time. The return element p5 is a waveform element whose voltage
returns from the contraction voltage VH to the reference voltage
VB. The voltage of the beginning of the inspecting drive pulse Pd
(the beginning of the preliminary expansion element p1) and the
voltage of the end of the inspecting drive pulse Pd (the end of the
return element p5) are set to the reference voltage VB. As the
inspecting drive pulse Pd, a drive pulse for printing can be used
or a pulse dedicated to the inspection processing can be used.
When the inspecting drive pulse Pd configured as described above is
applied to the piezoelectric element 16 of the inspection target
vibration portion, first, the inspection target vibration portion
is bent in a direction away from the nozzle plate 11 by the
preliminary expansion element p1, and accordingly the pressure
chamber 21 expands from a reference volume corresponding to the
reference voltage VB to an expansion volume corresponding to the
expansion voltage VL. An expansion state of the pressure chamber 21
is maintained for a certain period of time by the expansion hold
element p2. After a hold by the expansion hold element p2, the
inspection target vibration portion is bent inside the pressure
chamber 21 (toward the nozzle plate 11) by the contraction element
p3. Accordingly, the pressure chamber 21 is rapidly contracted from
the expansion volume to a contraction volume corresponding to the
contraction voltage VH. Thereby, the ink in the pressure chamber 21
is pressurized and the pressure vibration is generated in the ink.
Subsequently, the return element p5 is applied, so that the
inspection target vibration portion returns to a steady position
corresponding to the reference voltage VB. Accordingly, the
pressure chamber 21 expands and returns to the reference volume
corresponding to the reference voltage VB. When the inspection
target vibration portion is driven by the inspecting drive pulse Pd
of the present embodiment, ink may be or may not be ejected from
the nozzle 24.
On the other hand, the adjusting drive signal COM2 is a drive
signal that is constant at an adjustment voltage Vad. That is, the
adjusting drive signal COM2 is constant at an adjustment voltage
Vad over the entire period from the period T1 to the period T3. In
the present embodiment, the adjustment voltage Vad is set to the
expansion voltage VL of the inspecting drive signal COM1. However,
the adjustment voltage Vad may be a voltage different form the
expansion voltage VL according to the degree of adjustment. The
adjusting drive signal COM2 is a signal that maintains a deformed
state of an adjusting vibration portion constant by continuously
applying a constant voltage (adjustment voltage Vad) to the
adjusting vibration portion described later at least in the
detection period (period T3) of the inspection target vibration
portion. The adjusting drive signal COM2 is not limited to a signal
formed from only the adjustment voltage Vad, but may have an
element where a voltage varies as described below.
Here, after the inspection target vibration portion is driven in
the period T2 by the inspecting drive pulse Pd of the inspecting
drive signal COM1, a constant reference voltage VB is continuously
applied to the piezoelectric element 16 of the inspection target
vibration portion. However, the inspection target vibration portion
is vibrated by the pressure vibration (residual vibration)
generated in the ink in the pressure chamber 21. Thereby, an
electromotive force based on the vibration is generated in the
piezoelectric element 16 of the inspection target vibration
portion. The vibration detection circuit 38 obtains an
electromotive force signal Sc (detection signal) of the
piezoelectric element 16. In the case of abnormality such as a case
of a so-called missing dot where ink is not ejected from the nozzle
24 and a case where even if ink is ejected from the nozzle 24, the
amount of ink or a flying speed of ink is extremely lower than
those ejected from a normal nozzle 24, a periodical component and
an amplitude component of the aforementioned detection signal are
different from a vibration period (hereinafter, reference vibration
period) and an amplitude of normal time which are acquired in
advance. A detection method of ejection abnormality based on the
electromotive force signal Sc has been publicly known, so that
detailed description will be omitted. However, it is possible to
detect ejection abnormality due to ink thickening and/or bubbles by
the detection method.
By the way, the aforementioned reference vibration period is a
value acquired under a predetermined condition (temperature,
humidity, and the like) in an inspection stage before the printer 1
is shipped from a factory. However, the recording head 2 of the
present embodiment is formed by bonding a plurality of substrates
with an adhesive or the like, so that due to, for example,
manufacturing variation and extrusion of adhesive to a flow path
(pressure chamber 21), the vibration period of vibration portion
corresponding to the nozzle 24 is different from the reference
vibration period depending on the nozzle 24. As a result, the
vibration periods may vary between the nozzles 24. Therefore, the
printer 1 according to the invention is configured so that the
degree of deformation (amount of bending/magnitude of bending) of
the adjusting vibration portion is adjusted by the adjusting drive
signal COM2 (second drive signal) when the piezoelectric element 16
of the inspection target vibration portion is driven and thereby
inspection is performed in a state where the vibration period of
the inspection target vibration portion is matched to the reference
vibration period. A difference from the reference vibration period
of each piezoelectric element 16 is acquired in advance in an
inspection stage before shipment from a factory and stored in, for
example, the storage unit 34. When the piezoelectric element 16 is
driven as the inspection target vibration portion, the adjustment
voltage Vad of the adjusting drive signal COM2 is set based on the
difference stored in the storage unit 34.
FIGS. 5 to 7 are schematic diagrams of the recording head 2 for
explaining the inspection processing and are cross-sectional views
in a nozzle row direction. Here, among the three piezoelectric
elements 16a to 16c adjacent to each other shown in FIGS. 5 to 7,
the piezoelectric element 16a located at the center is an
inspection target piezoelectric element (corresponding to a first
piezoelectric element in the invention), and the inspection target
piezoelectric element and the flexible plane 22 corresponding to
the inspection target piezoelectric element are the inspection
target vibration portion (corresponding to a first vibration
portion in the invention). The piezoelectric elements 16b and 16c
adjacent to the piezoelectric element 16a with the partition wall
25, which is located at both sides of the piezoelectric element
16a, in between are adjusting piezoelectric elements (corresponding
to second piezoelectric elements in the invention) that adjust the
vibration period of the inspection target vibration portion, and
the adjusting piezoelectric element and the flexible plane 22
corresponding to the adjusting piezoelectric element are the
adjusting vibration portion (corresponding to a second vibration
portion in the invention).
As shown in FIG. 5, in the first period T1, the reference voltage
VB of the inspecting drive signal COM1 is applied to the
piezoelectric element 16a which is the inspection target vibration
portion, and the adjustment voltage Vad of the adjusting drive
signal COM2 is applied to the piezoelectric elements 16b and 16c.
In the first period T1, the piezoelectric element 16a which is the
inspection target vibration portion is bending toward the inside of
the pressure chamber 21 (toward the nozzle plate 11) corresponding
to the reference voltage VB. On the other hand, the central portion
in the width direction of the adjusting vibration portion (the
piezoelectric elements 16b and 16c and the flexible planes 22
thereof) to which the adjustment voltage Vad is applied bends away
from the nozzle plate 11 (in a direction indicated by void arrows
in FIG. 5), and becomes nearly in parallel with the upper opening
surface of the pressure chamber 21 (slightly bends into the
pressure chamber 21 instead of becoming in parallel with the upper
opening surface). In this way, the adjustment voltage Vad of the
adjusting drive signal COM2 is continuously applied to the
piezoelectric elements 16b and 16c and the amount of bending of the
adjusting vibration portion is adjusted. The adjusting vibration
portions bend, so that the flexible plane 22 corresponding to the
inspection target vibration portion is pulled from both sides (from
the pressure chambers 21b and 21c on both adjacent sides) and a
tensile force (tension) is applied to the flexible plane 22. The
amount of bending of the adjusting vibration portion is adjusted,
so that the magnitude of the tension changes.
Specifically, when the tension applied to the flexible plane 22 of
the inspection target vibration portion increases, the hardness
(compliance C [mm/N]) of the flexible plane 22 of the inspection
target vibration portion becomes greater than the original hardness
of the flexible plane 22 of the inspection target vibration portion
of when the inspection target vibration portion is independently
driven. On the other hand, when the tension applied to the flexible
plane 22 of the inspection target vibration portion decreases, the
hardness of the flexible plane 22 of the inspection target
vibration portion becomes smaller than the original hardness of the
flexible plane 22 of the inspection target vibration portion of
when the inspection target vibration portion is independently
driven. The vibration period of the inspection target vibration
portion changes according to the compliance C. In other words, the
vibration period of the inspection target vibration portion changes
according to the change of hardness of the flexible plane 22 of the
inspection target vibration portion. For example, when it is
assumed that the tension applied to the flexible plane 22 of the
inspection target vibration portion becomes the smallest when the
adjustment voltage Vad applied to the piezoelectric element 16 of
the adjusting vibration portion is the ground voltage (GND), the
higher the adjustment voltage Vad, the greater the tension applied
to the flexible plane 22 and the smaller the compliance C, so that
the vibration period of the inspection target vibration portion
further decreases. The closer the adjustment voltage Vad of the
adjusting drive signal COM2 is to the ground voltage (GND), the
smaller the tension applied to the flexible plane 22 and the
greater the compliance C, so that the vibration period of the
inspection target vibration portion further increases. Therefore,
when a unique vibration period of each vibration portion including
the piezoelectric element 16 and the flexible plane 22
corresponding to the piezoelectric element 16 is different from the
reference vibration period due to manufacturing variation and the
like, it is possible for the adjusting vibration portion to adjust
(correct) the unique period so that the unique period becomes close
to the reference vibration period. In the present embodiment, the
inspection target vibration portion and the adjusting vibration
portion are adjacent to each other with one partition wall 25 in
between, so that it is possible to more efficiently adjust the
tensile force applied to the flexible plane 22 of the inspection
target vibration portion, which is caused by deformation of the
adjusting vibration portion.
As shown in FIG. 6, in the second period T2 which is the vibration
generation period, the inspecting drive pulse Pd of the inspecting
drive signal COM1 is applied to the piezoelectric element 16a of
the inspection target vibration portion and the adjustment voltage
Vad of the adjusting drive signal COM2 is continuously applied to
the piezoelectric elements 16b and 16c of the adjusting vibration
portions. Then, the inspection target vibration portion vibrates
according to the inspecting drive pulse Pd, so that the pressure
vibration is generated in the ink in the pressure chamber 21a
corresponding to the inspection target vibration portion. Next, in
the third period T3 which is the detection period, the constant
reference voltage VB is continuously applied to the piezoelectric
element 16a of the inspection target vibration portion and the
constant adjustment voltage Vad is continuously applied to the
piezoelectric elements 16b and 16c of the adjusting vibration
portions. Then, as shown in FIG. 7, the inspection target vibration
portion is freely-vibrated by the pressure vibration (residual
vibration) generated in the ink in the pressure chamber 21a
corresponding to the inspection target vibration portion. Thereby,
an electromotive force based on the free vibration is generated in
the piezoelectric element 16 of the inspection target vibration
portion. In the third period T3, the vibration detection circuit 38
obtains an electromotive force signal Sc (detection signal) of the
piezoelectric element 16a of the inspection target vibration
portion. Then, the CPU 35 determines presence or absence of
abnormality of ink ejection of the nozzle 24 to be inspected by
comparing periodical components, amplitude components, and the like
between the electromotive force signal Sc and the reference
vibration period. In this way, in the printer 1 according to the
invention, the inspection is performed in a state in which the
vibration period of the inspection target vibration portion is set
to the reference vibration period. Therefore, it is possible to
improve inspection accuracy. Further, in the present embodiment,
the adjusting vibration portion does not vibrate in a period of
time in which the inspection target vibration portion vibrates in
the detection period and a constant shape of the adjusting
vibration portion is maintained, so that it is suppressed that the
vibration of the adjusting vibration portion is superimposed on the
vibration of the inspection target vibration portion to cause
adverse effects.
By the way, the viscosity of the ink changes when the environmental
temperature (the temperature around (inside) the printer 1, in
particular, the temperature near the nozzle 24) changes, and the
vibration period of the ink during inspection also changes
according to the viscosity of the ink, so that the inspecting drive
signal COM1 is corrected according to the environmental temperature
detected by the temperature sensor 40. More specifically, in a
configuration where the temperature when the reference vibration
period is acquired (for example, 25.degree. C.) is defined as a
reference temperature and the reference voltage VB is set for the
inspecting drive signal COM1 at the reference temperature, when the
temperature becomes higher than the reference temperature (for
example, the temperature becomes 40.degree. C.), as shown in FIG.
4, the reference voltage VB is corrected to the reference voltage
VB1 lower than the reference voltage VB. When the temperature
becomes lower than the reference temperature (for example, the
temperature becomes 15.degree. C.), the reference voltage VB is
corrected to the reference voltage VB2 higher than the reference
voltage VB at the reference temperature. When the value of the
reference voltage VB which is a voltage at the beginning and the
end of the inspecting drive pulse Pd changes according to the
temperature, the degree of deformation of the inspection target
vibration portion (in particular, the degree of deformation in the
third period T3 which is the inspection period) also changes, so
that even when the vibration period of the inspection target
vibration portion is the same as the reference vibration period at
the reference temperature, the vibration period changes from the
reference vibration period due to a temperature change. Therefore,
a difference between the vibration period of each piezoelectric
element 16 and the reference vibration period is acquired for each
temperature and stored in the storage unit 34, and when the
piezoelectric element 16 is driven as the inspection target
vibration portion, temperature is acquired by the temperature
sensor 40 and the adjustment voltage Vad of the adjusting drive
signal COM2 is set based on the difference stored in the storage
unit 34. Thereby, even when the environmental temperature changes,
the inspection is performed in a state in which a unique vibration
period of the inspection target vibration portion is set to the
reference vibration period. Therefore, it is possible to improve
inspection accuracy.
In the present embodiment, a configuration is illustrated where the
tension applied to the inspection target vibration portion is
adjusted by setting the adjustment voltage Vad lower than the
reference voltage VB. However, the tension adjustment is not
limited to this, and it is possible to employ a configuration where
the tension applied to the inspection target vibration portion is
adjusted by setting the adjustment voltage Vad higher than the
reference voltage VB. That is, in this case, the higher the
adjustment voltage Vad, the more the central portion in the width
direction of the adjusting vibration portion bends into the
pressure chamber 21 (toward the nozzle plate 11). Thereby, a
greater tension is applied to the inspection target vibration
portion.
The adjusting vibration portion does not necessarily have to be
used to eject ink. That is, the adjusting vibration portion only
have to include at least the piezoelectric element 16, the flexible
plane 22, and the pressure chamber 21. The pressure chamber 21 may
be a so-called dummy pressure chamber that does not communicate
with the nozzle 24. The size of the dummy pressure chamber need not
be the same as that of the pressure chamber 21 used to eject ink.
Further, the dummy pressure chamber need not be filled with ink,
but may be filled with air. In the first embodiment described
above, a configuration is illustrated where the nozzles 24 are
provided in a row shape and accordingly the pressure chambers 21
are arranged side by side in parallel. However, the configuration
is not limited to this, and the invention can be applied to, for
example, a configuration where the pressure chambers and the
vibration portions corresponding to the pressure chambers are
arranged in a matrix shape. Among the vibration portions arranged
in this way, a vibration portion located in a position where the
vibration portion can apply tension to the inspection target
vibration portion can function as the adjusting vibration
portion.
FIG. 8 is a waveform chart for explaining a configuration of an
inspecting drive signal COM1a and adjusting drive signals COM2a to
2c in a second embodiment. The inspecting drive signal COM1a shown
in the uppermost section in FIG. 8 is divided into four periods,
which are a first period T1, a second period T2, a third period T3
and a fourth period T4. An inspecting drive pulse Pd' is generated
in the second period T2. In the first period T1, the third period
T3, and the fourth period T4, the voltage of the inspecting drive
signal COM1a is constant at the reference voltage VB. Among the
periods T1 to T4, the second period T2 is a vibration generation
period in which pressure vibration is generated in the ink in the
pressure chamber 21, and the fourth period T4 is a detection period
in which the pressure vibration of ink generated in the second
period T2 is detected. The inspecting drive pulse Pd' generated in
the second period T2 is an inverted trapezoidal wave that varies
from the reference voltage VB to an expansion voltage VL lower than
the reference voltage VB and thereafter returns to the reference
voltage VB.
The adjusting drive signal COM2a is a drive signal having an
adjustment pulse Pa1 of an inverted trapezoidal wave that varies
from the reference voltage VB to the adjustment voltage Vad (the
expansion voltage VL in the present embodiment) lower than the
reference voltage VB in the first period T1, maintains the
adjustment voltage Vad in the second period T2, the third period
T3, and the fourth period T4, and there after varies from the
adjustment voltage Vad to the reference voltage VB. That is, the
adjusting drive signal COM2a is different from the adjusting drive
signal COM2 that is constant at the adjustment voltage Vad
according to the first embodiment in that the adjusting drive
signal COM2a has an element in which voltage varies. A waveform
element in which voltage varies from the reference voltage VB to
the adjustment voltage Vad is not limited to a waveform element
generated at an illustrated timing, but may be generated, for
example, before the fourth period T4, which is the detection
period, as shown by dashed lines. When the inspection target
vibration portion is driven by the inspecting drive signal COM1a,
the constant adjustment voltage Vad is continuously applied to the
piezoelectric element 16 of the adjusting vibration portion in the
fourth period T4 which is the detection period. Also in this
configuration, in the same manner as in the first embodiment, it is
possible to adjust the unique vibration period of the inspection
target vibration portion. The adjustment voltage Vad may be
different from the expansion voltage VL.
The adjusting drive signal COM2b is a drive signal having a first
stage pulse Pa2a having the same shape as that of the inspecting
drive pulse Pd' that varies from the reference voltage VB to the
adjustment voltage Vad (expansion voltage VL) and thereafter
returns to the reference voltage VB in the second period T2 and a
second stage pulse Pa2b having an inverted trapezoidal wave that
varies from the reference voltage VB to the adjustment voltage Vad
again in the third period T3, maintains the adjustment voltage Vad
constant in the fourth period, and thereafter returns from the
adjustment voltage Vad to the reference voltage VB. The adjusting
drive signal COM2b can amplify the amplitude of the vibration of
the inspection target vibration portion by applying the first stage
pulse Pa2a having the same shape as that of the inspecting drive
pulse Pd' to the adjusting vibration portion at a timing when the
inspecting drive pulse Pd' of the inspecting drive signal COM1 is
applied to the inspection target vibration portion. In other words,
the inspection target vibration portion and the adjusting vibration
portion are driven in a similar manner and their vibrations
resonate, so that the amplitude of the vibration of the inspection
target vibration portion is amplified. Thereby, it is possible to
further improve the detection accuracy. In this case, the greater
the number of the vibration portions that are driven at the same
time, the more difficult the bending of the partition wall 25 that
delimits the pressure chamber 21 corresponding to the inspection
target vibration portion when the inspection target vibration
portion vibrates, so that it is possible to further amplify the
vibration of the inspection target vibration portion. In the fourth
period T4 which is the detection period, the constant adjustment
voltage Vad is continuously applied to the piezoelectric element 16
of the adjusting vibration portion. Also in this configuration, in
the same manner as in the first embodiment, it is possible to
adjust the vibration period of the inspection target vibration
portion to match the reference vibration period.
The adjusting drive signal COM2c is a drive signal having an
adjustment pulse Pa3 that varies from the reference voltage VB to a
first adjustment voltage Vad1 in the first period T1, and then
maintains the first adjustment voltage Vad1 in the second period
T2, varies from the first adjustment voltage Vad1 to a second
adjustment voltage Vad2 slightly higher than the first adjustment
voltage Vad1 (Vad1<Vad2<VB) in the second period T3,
maintains the second adjustment voltage Vad2 in the fourth period
T4, and thereafter returns from the second adjustment voltage Vad2
to the reference voltage VB. That is, the adjusting drive signal
COM2c is different from the other adjusting drive signals in that
the adjusting drive signal COM2c has two different adjustment
voltages Vad1 and Vad2. In the adjusting drive signal COM2c, it is
possible to select either one of the first adjustment voltage Vad1
and the second adjustment voltage Vad2 as the adjustment voltage
applied to the adjusting vibration portion in the fourth period T4
by the pulse selection switch 37. For example, when setting the
adjustment voltage applied to the adjusting vibration portion in
the fourth period T4 to the first adjustment voltage Vad1, the
pulse selection switch 37 is set to a connection state and the
adjusting drive signal COM2c is applied to the adjusting vibration
portion in the first period T1 and the second period T2, and the
pulse selection switch 37 is set to a disconnection state at a
boundary between the second period T2 and the third period T3. The
piezoelectric element 16 behaves like a capacitor, so that the
voltage of the piezoelectric element 16 is maintained at the first
adjustment voltage Vad1 that is a voltage immediately before the
pulse selection switch 37 is disconnected. For example, when
setting the adjustment voltage applied to the adjusting vibration
portion in the fourth period T4 to the second adjustment voltage
Vad2, the pulse selection switch 37 is set to the connection state
so that the entire pulse Pa3 of the adjusting drive signal COM2c is
applied to the adjusting vibration portion in the periods T1 to T4.
Alternatively, the pulse selection switch 37 is set to the
disconnection state in the periods T1 to T3 and the pulse selection
switch 37 is switched to the connection state in the period T4. In
this way, a plurality of adjustment voltages are included in the
adjusting drive signal COM2c, so that it is possible to easily
select a more suitable adjustment voltage according to data of a
difference from the reference vibration period.
FIG. 9 is a waveform chart for explaining a configuration of a
drive signal COMs in a third embodiment. The upper waveform in FIG.
9 represents an original waveform of the drive signal COMs, the
middle waveform represents a waveform of the drive signal COMs
applied to the piezoelectric element 16 of the inspection target
vibration portion, and the lower waveform represents a waveform of
the drive signal COMs applied to the piezoelectric element 16 of
the adjusting vibration portion. In the embodiments described
above, the inspecting drive signal and the adjusting drive signal
are drive signals different from each other. On the other hand, in
the present embodiment, different from the embodiments described
above, one drive signal serves both as the inspecting drive signal
(first drive signal) and the adjusting drive signal (second drive
signal). A CH signal which is a control signal of the pulse
selection switch 37 is shown corresponding to the drive signal
COMs. The drive signal COMs is supplied in common to the
piezoelectric element 16 of the inspection target vibration portion
and the piezoelectric element 16 of the adjusting vibration portion
and a predetermined waveform element of the drive signal COMs is
applied by switching of the pulse selection switch 37.
The drive signal COMs shown in an upper section in FIG. 9 is
divided into four periods, which are a first period T1, a second
period T2, a third period T3 and a fourth period T4. In the first
period T1, the drive signal COMs varies from a first adjustment
voltage Vad1 which is the reference voltage VB to a second
adjustment voltage Vad2 (contraction voltage that causes the
pressure chamber 21 to contract) higher than the first adjustment
voltage Vad1. In the second period T2, an inspecting drive pulse
Pd'' of an inverted trapezoidal wave is generated, which varies
from the second adjustment voltage Vad2 to a third adjustment
voltage Vad3 (expansion voltage that causes the pressure chamber 21
to expand) between the second adjustment voltage Vad2 and the first
adjustment voltage Vad1 and returns from the third adjustment
voltage Vad3 to the second adjustment voltage Vad2. In the third
period T3, the drive signal COMs varies from the second adjustment
voltage Vad2 to the first adjustment voltage Vad1, and thereafter,
in the fourth period T4, the drive signal COMs is constant at the
first adjustment voltage Vad1 (reference voltage VB). Among the
periods T1 to T4, the second period T2 is a vibration generation
period in which pressure vibration is generated in the ink in the
pressure chamber 21, and the fourth period T4 is a detection period
in which the pressure vibration of ink generated in the second
period T2 is detected.
As shown in a middle section of FIG. 9, from an adjusting drive
signal COM2s, a constant component at the second adjustment voltage
Vad2 in the first period T1, the inspecting drive pulse Pd'' in the
second period T2, and a constant component at the second adjustment
voltage Vad2 in the third period T3 are selectively applied to the
piezoelectric element 16 of the inspection target vibration portion
by the pulse selection switch 37. As shown in a lower section of
FIG. 9, a constant component at the first adjustment voltage Vad1
in the first period T1 and the fourth period T4 is selectively
applied to the piezoelectric element 16 of the adjusting vibration
portion by the pulse selection switch 37, so that it is possible to
maintain the first adjustment voltage Vad1 through the periods T1
to T4 (solid line in FIG. 9). A constant component at the second
adjustment voltage Vad2 in the first period T1 and the third period
T3 is selectively applied to the piezoelectric element 16 of the
adjusting vibration portion by the pulse selection switch 37, so
that it is possible to maintain the second adjustment voltage Vad2
through the periods T1 to T4 (dashed line in FIG. 9). Further, a
constant component at the third adjustment voltage Vad3 in the
second period T2 is selectively applied to the piezoelectric
element 16 of the adjusting vibration portion by the pulse
selection switch 37, so that it is possible to maintain the third
adjustment voltage Vad3 through the periods T1 to T4 (dashed-dotted
line in FIG. 9). As described above, even when the drive signal
COMs common to the inspection target vibration portion and the
adjusting vibration portion is used, by selectively applying a
waveform component of the drive signal COMs, it is possible to
perform inspection by using the inspecting drive pulse Pd'' in the
inspection target vibration portion and it is possible to easily
select a more suitable adjustment voltage according to data of a
difference from the reference vibration period in the adjusting
vibration portion.
The configuration of the drive signal is not limited to those
illustrated in each embodiment, but it is possible to employ drive
signals of various waveforms. In short, any waveform can be
employed which can adjust the vibration period of the inspection
target vibration portion by driving the inspection target vibration
portion to generate pressure vibration in the ink in the pressure
chamber 21 in the inspection processing and applying a constant
adjustment voltage to the adjusting vibration portion at least in
the detection period to maintain a state where the adjusting
vibration portion is deformed.
FIGS. 10 to 12 are diagrams for explaining the other embodiments of
the invention. In the first embodiment described above, a
configuration is illustrated in which the piezoelectric elements
16b and 16c adjacent to the piezoelectric element 16a, which is a
detecting vibration portion, with one partition wall 25 in between
function as the adjusting vibration portion. However, the
configuration is not limited to this. For example, like a fourth
embodiment shown in FIG. 10, another piezoelectric element 16
(piezoelectric elements 16b and 16c) not related to detection or
adjustment may be arranged between the detecting vibration portion
(piezoelectric element 16a) and the adjusting vibration portion
(piezoelectric elements 16d and 16e). In short, the piezoelectric
element 16 and the flexible plane corresponding to the
piezoelectric element 16, which are in a positional relationship
where a tension is applied to the detecting vibration portion when
the piezoelectric element 16 and the flexible plane are driven as
the adjusting vibration portion, can be functioned as the adjusting
vibration portion.
Further, like a fifth embodiment shown in FIG. 11, it is also
possible to employ a configuration in which three or more (three
rows of more) piezoelectric elements 16b to 16e function as the
adjusting vibration portions with respect to one detecting
vibration portion. When much more adjusting vibration portions are
driven in this way, it is possible to cause much more tension
change on the detecting vibration portion. Thereby, it is possible
to secure a large adjustment range (in particular, to increase the
tension) of the vibration period and the like of the detecting
vibration portion.
Further, a piezoelectric element 41 in a sixth embodiment shown in
FIG. 12 is a stacked type element manufactured by cutting a
piezoelectric plate, where piezoelectric layers and electrode
layers (none of them are shown) are alternatively stacked, into a
comb-teeth shape, and is a piezoelectric element of a so-called
vertical vibration mode of an electric field transversal effect
type, which expands and contracts in a direction perpendicular to
the stacked direction (electric field direction). For example, in a
vibration period of time of the piezoelectric element 41a that
functions as the detecting vibration portion, piezoelectric
elements 41b and 41c and the flexible planes 22 corresponding to
the piezoelectric elements function as the adjusting vibration
portion and can adjust the vibration period of the detecting
vibration portion. In this example, the lower a voltage of an
adjustment signal applied to the adjusting vibration portion, the
more the adjusting vibration portion expands, and accordingly the
flexible plane 22 is displaced into the pressure chamber 21.
Thereby, the flexible plane 22 of the detecting vibration portion
is pulled from both sides and a tension is applied to the flexible
plane 22. Also in this configuration, it is possible to adjust the
vibration period and the like of the detecting vibration portion in
the same manner as in each embodiment described above.
The invention can be applied to any liquid ejecting apparatus,
which drives a piezoelectric element to eject liquid from a nozzle
by pressure vibration generated in ink in the pressure chamber,
such as various ink jet type recording apparatuses including not
only a printer, but also a plotter, a facsimile apparatus, and a
copy machine, and liquid ejecting apparatuses other than the
recording apparatuses, such as, for example, a display
manufacturing apparatus, an electrode manufacturing apparatus, and
a chip manufacturing apparatus.
* * * * *